BIG Day Out organisers this morning announced plans to cancel one of the event's two Sydney shows in January.

The show scheduled for January 27 will now "be merged" into one show on January 26, Australia Day.

The event has hosted two back-to-back events in Sydney since 2010.

"While we are looking into a possible expanded capacity for the 26 January, given the merge of the two shows, tickets to January 26 are anticipated to sell out much earlier so do not delay if you have not already purchased," Ken West said in a statement.

Fans who purchased tickets for January 27 can either go to the festival the day before, get a full refund or exchange their ticket for one of the other shows in Melbourne, Adelaide, Perth or the Gold Coast.

The downsizing follows the Harvest Festival's cancellation and the news last week that Soundwave promoter AJ Maddah had bought into Big Day Out.